Xerographic developing apparatus



June 18, 1963 c. L. HUBER XEROGRAPHIC DEVELQPING APPARATUS 4 Sheets-Sheet 1 Filed April 4, 1960 DEVELOPMENT ZONE AEROSOL HANDLING POWDER REGULATING CLOUD VALVE GENERATOR COMPRESSOR FIG. 2

INVENTOR. CHARLES L. HUBER fin A TTQPNE V June 18, 1963 c. HUBER 3,094,248

XEROGRAPHIC DEVELOPING APPARATUS Filed April 4, 1960 4 Sheets-Sheet 2 INVENTOR. CHARLES L. HUBER ATTORNEY June 18, 1963 Filed April 4, 1960 C. L. HUBER XEROGRAPHIC DEVELOPING APPARATUS 4 Sheets-Sheet 3 INVENTOR. CHARLES L. HUBER yan/.

A T TORNE Y June 18, 1963 c. HUBER 3,094,248

XEROGRAPHIC DEVELOPING APPARATUS CHARLES L. HUBER A7 TORNE V United States Patent 3,094,248 XEROGRAPHIC DEVELOPING APPARATUS Charles L. Huber, Byron, N.Y., assignor to Xerox Corporation, a corporation of New York Filed Apr. 4, 1960, Ser. No. 19,845 5 Claims. (Cl. 222-193) This invention relates to the field of xerography and, particularly, to an improved powder cloud generator metering apparatus for powder cloud development of Xerographically produced images. More specifically, the invention relates to improvements in powder cloud generators of the type disclosed in Hayford et al. Patent 2,862,646, issued December 2, 1958, and in copending Huber application Serial No. 737,584, filed May 26, 1958.

In the process of xerography, for example, as disclosed in Carlson Patent 2,297,691, issued October 6, 194 2, a Xerographic plate comprising a layer of photoconductive insulating material on a conductive backing is given a uniform electric charge over its surface and is then exposed to the subject matter to be reproduced, usually by conventional projection techniques. This exposure discharges the plate areas in accordance with the radiation intensity that reaches them, and thereby creates an electrostatic latent image on or in the photoconductive layer. Development of the latent image is effected with an electrostatically changed, finely divided material, such as an electroscopic powder, which is brought into surface contact with the photoconductive layer and is held thereon electrostatically in a pattern corresponding to the electrostatic latent image. Thereafter, the developed xerographic image is usually transferred to a support surface to which it may be fixed by any suitable means.

Two methods of image development are in common use. One method is described in Walkup Patent 2,618,551 and is known as cascade development, and is in general use for line copy development. 'In this technique the powder is mixed with a granular material, and this twocomponent developer is poured or cascaded over the plate surface. The function of the granular material is to improve the flow characteristics of the powder and to produce, on the powder, by tri'boelectrification, the proper electrical charge so that the powder 'will be attracted to the image. More exactly, the function of the granular material is to provide the mechanical control to the powder, or to carry the powder to an image surface and, simultaneously, to provide almost complete homogeneity of charge polarity.

The other form of development is known as powder cloud development and is in general use for continuous tone development. In this technique of development a dispersion of electrically charged powder particles in an vaeriform fluid is passed to the surface bearing the electrical image and particles are drawn from the aeriform fluid dispersion to form a powder image on the plate. The earliest form of development of this type is disclosed and described in Carlson Patent 2,221,77 6 wherein a rotating vane wheel or propeller is used to stir up powder in a chamber, thereby creating a cloud of particles for presentation to the electrostatic image.

Generally in powder cloud generating apparatus there is included a powder source, means to create a cloud of powder in aeriform fluid, means to convey the cloud to a surface carrying an electrostatic image, and means to electrostatically charge the powder in the cloud before it reaches the surface. Such devices, which include one or a number of the above elements, and which are used to take powder from a source whether it be a mound of powder or .whether it be in other shapes or forms, and convert the powder to an aerosol of powder in aeriform fluid, is herein and generally in the art referred to as a powder cloud generator or as a cloud generator, as deice 2. scribed in Hayford Patent 2,812,883 and in the abovereferred-to Hayford et al. Patent 2,862,646.

An object in the art of xerography, as in any art concerned with image reproduction, is that of uniformly developing high quality copy. Means of obtaining this objective, while using powder cloud development, is through the uniform and constant presentation to the electrostatic latent image on a surface of a powder cloud of fine developer powder particles uniformly and densely dispersed throughout.

The powder cloud generating devices of the prior art, as exemplified by the disclosure in Hayford Patent 2,86%- 646, usually consists of a powdered support rotatably journaled and enclosed within a suitable pressure housing. At one point or loading area on the surface of the powder support, there is manually positioned a quantity of raw or bulk powder cloud particles. These particles are held in position by a scraper or meter blade, which also acts to meter out a layer of powder to the surface of the powder support as it moves or rotates beneath the powder supply and first scraper. The particular surface of the support is one which loads uniformly as it passes beneath the powder supply. Compressed aeriform fluid is flowed into the housing at one point, and powder dispersed in the aeriform fluid flows out of the housing through a suitable output tube. An output orifice is connected within the housing to the output tube and is positioned at a distance above the surface of the support. Particles on the surface of the support are entrained in the flow of the aeriform fluid traveling from the housing out through the output orifice and output tube, thereby creating at the output end of the output tube an aerosol of powder particles.

In the prior art devices, of the type described, the amount of time in which a unit can be operated at a given dispensing rate is dependent upon the amount or charge of powder deposited on the support. When the charge is dispensed, the unit must be de-pressurized before the housing can be opened to permit the placing of a new charge of powder on the support. This operating technique is time-consuming.

Although the operating time of a device, of this type, may be extended Within apparent limits by increasing the amount of powder in a charge, this mode of operation severely limits the operating efficiency and accuracy of the unit; the accuracy of the unit being affected because as the amount of powder on the support increases, the powder at the bottom of the pile will become more dense, thereby affecting the uniform loading of the support.

It is, therefore, an object of this invention to improve upon powder cloud generators so that a uniform and dense dispersion of powder particles in an aeriform fluid can be created for a relatively long period of time.

A further object of this invention is to provide a powder cloud generator in which powder is uniformly deposited upon a powder support from where it is metered and entrained in the flow of an aeriform fluid out of the powder cloud generator.

Another object of this invention is to provide an improved powder dispenser capable of dispensing a uniform metered quantity of powder particles.

For a better understanding of this invention, together with further objects thereof, reference is had to the following description taken in connection with the accompanying drawings, wherein:

FIG. 1 is a block diagram of elements which generally appear in xerographic cloud generating apparatus for use in developing electrostatic latent images;

FIG. 2 is a top view of the powder cloud generator with parts broken away to show the internal structural elements of the device;

FIG. 3 is a cross-sectional view of the powder cloud generator taken along line 33 of FIG. 2;

FIG. 4 is a detail sectional view of the mounting means for the meter blades taken along line 4-4 of FIG. 2;

FIG. 5 is a perspective view, with parts broken away, of the powder dispenser element of the powder cloud generator of FIGS. 2 and 3; and

FIG. 6 is a cross-sectional view of a modified powder dispenser and powder cloud generator.

Referring now with more particularity to the drawings, in FIG. 1 is shown a block diagram of elements which compose cloud-creating apparatus for development of electrostatic images. As is indicated in this diagram, compressed aeriform fluid is fed from compressor 11 to a powder cloud generator 13 through a regulatlng valve 12, and the output of the powder cloud generator is fed through aerosal handling means 15 and then to the development zone 16 Whereat developer particles are passed for development purposes to a surface carrying an electro static latent image.

The source of compressed or pressurized aeriform fluid may be any suitable source, such as, for example, an air pump or like pressure generating member or a suitable pressurized gas container. Such containers are readily available on the commercial market in the form of gas capsules of carbon dioxide or the like under pressure, in the form of bombs or the like of gas such as fluorochloroalkanes, which are available under the general family name of Freon. Similarly, a suitable system may comprise a pump or generating means optionally in combination with a pressure chamber whereby fluctuations in pressure may be limited or avoided.

Regulating valve 12 is used to control the rate of flow of aer-iform fluid from compressor 11 to powder cloud generator 13 and also to control the pressure of gas supplied to the powder cloud generator. The powder cloud generator, which is the next block in this diagram following regulating valve 12, is used to create an aerosol of powder in air. It may be supplied with powder in what may be termed the raw or bulk form, that is, powder taken directly from a container and directly supplied in that form without treatment. It may also be supplied with powder which is first treated and then placed in position in the generator. The particular powder used is dependent on a number of factors such as other elements used in the cloud-creating apparatus, the form of xero graphic development, the desired quality of final copy, and the like.

The aerosol handling block 15 of the diagram appearing in FIG. 1 may represent any number of means and apparatus for imparting an electrostatic charge or deagglomerating the individual powder particles in the aerosol supplied from the powder cloud generator. Charging and deagglomeration of particles may be accomplished by turbulently flowing them through fine capillary tubes, such as disclosed in copending Ricker applicaion Serial No. 353,520, filed May 7, 1953, now Patent No. 2,943,950. Charging may be accomplished by passing the aerosol of powder in air through a corona discharge zone, or the like.

The aerosol composed of charged particles in gas is next supplied, as indicated by the block diagram, to development zone 16. Generally, this zone includes a means for expanding the aerosol to a cloud, and optionally this may be done by leading the air from tubes or the like to a larger area where the aerosol expands, creating the cloud of charged developer particles in gas. It is also feasible and sometimes desirable to use the particles in aerosol form without expansion.

-In order to develop a true copy of the original image, it is generally desirable to develop against gravitational pull in that the electrostatic charges on the plate surface truly represent the pattern of the image projected to the plate surface, and allowing gravitational forces to operate in causing deposition of powder particles may result in a distorted reproduction. Also in causing the particles to deposit against the pull of gravity, deposition on the imagebearing surface of agglomerates is reduced. This may be accomplished by positioning the plate with the imagebearing surface facing downward and creating a cloud beneath it. In some instances particles deposited because of other forces may be removed during the dvelopment process through the use of such techniques as directing slight air currents or winds to the plate surface. Such winds or currents should be suflicient to remove particles not held in place due to electrostatic forces, but should be limited so that particles electrostatically held in plate are not affected.

Reference is now had to FIGS. 2 to 4, inclusive, wherein is shown a preferred embodiment of a powder cloud generator 13 according to this invention. The flanged, cup-shaped body or casing 20 has mounting lugs 21 formed integrally therewith for supporting the unit on a structural element (not shown) of the xerographic machine and an inlet duct or air inlet opening 55 for connection to a source of aeriform fluid under pressure. The shaft 22, which may be driven by any suitable power means (not shown), is journaled in double sealed bearings 23 and 24 mounted in the hub 25 of the body or casing 20. A groove 26 extends along the bored wall of the hub 25 to permit equalization of pressure on both sides of the bearing 23, while the bore opening in the hub 25 is sealed by oil seals 27 positioned between the bearings 23 and 24.

A cup-shaped powder carrier element 28 is rotatably positioned in the casing 20 and is secured against a shoulder of the shaft 22 by means of the washer 29 and a screw fastener 30. The powder carrier element 28 consists of a backing plate 31, the upper surface of which is faced with a skin or support 32 having numerous interstices in the surface thereof for carrying powder particles, suitable materials, such as cotton flannel, for the skin or support 32 being more fully described in above-referenced Hayford et a1. Patent 2,862,646. Shell 33, fastened by suitable means to backing plate 31, is used to retain powder on the backing plate, and with the pins 34 secured in the upper face edge of the shell, it is used as a cog wheel for driving powder dispenser 31, as described hereinafter.

First and second meter blades or scrapers 35 and 36, respectively, are adjustably positioned over the skin or support 32 in the powder carrier element 28, for metering powder across the surface of the powder carrier element 28, and first and second brushes 37 and 38, respectively, are spring mounted against the suface of the skin or support 32 to agitate powder particles deposited on the surface thereof. To accomplish this, bearing blocks 39, which rotatably carry adjustment screws 40 positioned by retaining rings 41 are fastened as by soldering to meter blade 36. Internally threaded blocks 42 and 43 are secured by soldering to the plate 44, the block 42 also supporting on a shoulder thereof a brush carrier 45 to which brush 37 is rotatably secured. The meter blade 35 is secured to the plate 44 by threading the adjustment screws 40 into the blocks 42 and 43.

The assembly of the meter blade 36 to the plate 44 is similar to the assembly of meter blade 35 to the plate 44, except that the brush carrier 46 is supported by block 42, the brush carrier 46 rotatably supporting brush 38. By means of the adjustment screws 40, the meter blades 35 and 36 can be adjustably positioned relative to the surface of the skin or support 32, and the position can be maintained by locking the adjustment screws 40 against further movement by nuts 47.

The plate 44, carrying the meter blades 35 and 36 and the brushes 37 and 38, is fastened by machine screw 49 and lockwasher 50, to yoke 48 secured by fasteners 53 to the shoulder 51 formed in the flange 52 of the body or casing 20. Apertures 54 in the yoke 48 permit access from the top to the nuts 47 and adjustment screws 40.

The open end of the casing or body 20 is closed by the cover plate 60 held in position by lockwashers 61, and

bolts 62, and sealed by O-ring :gasket 64 held in a suitable annular recess in the upper face of the flange 52. The cover plate 60 secured to the body or casing 20 forms a housing, generally designated 77, which surrounds and encompasses the internal elements. The cover plate 60 is provided with an opening 65 located so that powder material may be supplied to the powder carrier element 28 in front of the meter blade 35.

The cover plate 60 is also provided with a threaded opening 68 receiving an externally threaded hollow cylinder 70 adjustably secured by lock nut 71 and sealed by gaskets 72 and 73 held in suitable annular recesses in the locking nut 71 and cover plate 60, respectively. A bored output tube 74 adapted to be secured to a discharge conduit (not shown) is fastened in the upper portion of the hollow cylinder 70, while a pick-up tube 75, in which a relatively large number of output orifices 76 are formed, is secured in the bottom portion of the hollow cylinder 7 In the prior art devices, in order to ope-rate for a reasonable period of time, it was necessary to place a large mass of powder on the support in front of meter blade 35 through opening 65 in cover plate 60, the opening then being closed before operation of the powder cloud generator. Thus, it is seen that the amount of developer powder particles placed in front of meter blade 35 would depend on the amount of continuous use desired of the powder cloud generator and, also, on the shape and size of this meter blade, since the latter determines how much powder the meter blade will retain. However, to operate this type of powder cloud generator for even an hour to develop continuous tone images on a relatively narrow xerographic plate requires a substantial quantity of powder be placed on the surface of the support. This not only overloads the support surface, but the larger the mass of powder placed thereon the greater the variation in the density or compactness of the powder mass. This variation in density of the powder mass affects the amount of powder metered by the meter blades.

To permit continued operation and to permit more accurate metering of powder, the powder cloud generator of the invention includes a powder dispenser to feed additional powder to the support of the powder carrier element, the powder dispenser being enclosed or formed as part of an enclosure whereby it may be pressurized to the same degree as the interior of the main casing of the generator.

To continuously teed additional powder particles onto support 32 of powder carrier element 28 and to control the amount of powder particles fed thereon, a powder dispenser, generally designated 81, is mounted on cover plate 60 over opening 65 therein.

The powder dispenser 81 consists of flanged bearing bracket 82 adapted to fit within the counterbored portion of the cover plate forming opening 65 to support shaft 83. Shaft 83 journalled vertically by bearings 84 secured in the bore of flanged bearing bracket 82 by snap rings 85, has a dispensing platform 86 mounted at its upper end and a cog wheel 87 at its lower end. Each of these latter two elements is fastened to shaft 83 by means of taper pins 88 whereby they will rotate with the shaft. Dispensing platform 86, usually made circular in form, has its upper surface faced preferably with a powder support 89 similar to support 32, the powder support 89' being held in place by ring 90 secured in a suitable manner to the stepped peripheral surface of the dispensing platform. Cog wheel 87, consisting or hub 91 having pins or teeth 92 secured around its peripheral edge, is positioned so that the pins 92 thereon will be engaged by the vertical pins 34 on shell 33 as it is rotated.

Open-ended dispenser cylinder or hopper 93 enclosing the dispensing platform is secured at its bottom end by screws 94 to the outer'hub portion of bearing bracket 82, the inside diameter of this cylinder being sufliciently large to permit the dispensing platform to rotate freely therein.

The dispenser cylinder 93 and dispensing platform 86, with the powder support 89 thereon, forms a reservoir for a supply of powder particles to be forwarded in metered quantities to powder carrier element 28.

Within the dispenser cylinder 93 there is mounted, by means of screws 95, a metering blade 96 and a dispensing blade 97. The bottom edge of metering blade 96 is positioned sufiiciently above the surface of the dispensing support, for example, 4 inch to inch, to permit the desired quantity of powder carried by the rotating powder support 89 to pass under this metering blade. The lower edge of dispensing blade 97 is positioned as close as possible to the dispensing support, without of course being in contact therewith with sufiicient force to tear off the powder support, to scrape the metered powder to the edge of the dispensing support, as it is rotated therebeneath, whereby powder is finally forced over the peripheral edge of the dispensing support through an opening or powder outlet 108 in the side Wall of the hopper opposite powder support 89 and adjacent these blades from whence it will fall through the apertures 98 in the bearing bracket onto the support 32 of powder carrier element 28.

Although any suitable means may be provided to permit adjustment of these blades with respect to the top of the dispensing support, limited adjustment of these blades in the embodiment disclosed is provided by enlargement of the screw holes in the side wall of the hopper to permit screws to be moved in a limited vertical path.

Since it is desirable that only metered quantities of powder particles enter the area enclosed by dispensing blade 97, metering blade 96 and a portion of the wall of dispenser cylinder 93, that is, powder carried by powder support 89 under metering blade 96 as this support is rotated in the direction of the arrow in FIG. 5, suitable means should be provided to prevent unmetered quantities of powder from entering this area, as, for example, by extending the dispensing blade and metering blade to the top of the dispenser cylinder, as shown in the preferred embodiment.

The above-described elements of the owder dispenser are enclosed within a dispenser housing 101 and secured thereto by screws 1G2 passing through suitable apertures in the flanged portion of bearing bracket 82 into the flanged bottom end of the dispenser housing. The dispenser housing is closed at its upper end by threaded closure plate 103 and sealed by O-ring 104 placed in a suitable annular groove in the top of the dispenser housing to be engaged by the flanged portion of the closure plate 103.

Bolts 105 and 166 passing through the flanged end of the dispenser housing secure this assembly to the cover plate 60 in position over the opening 65 therein, the assembly being sealed by O-ring gasket 107 positioned in a suitable annular groove in the cover plate.

Casing 25 cover plate 60, dispenser housing 101 and closure plate 183 form an air-tight housing for the remaining elements of the apparatus, ingress for aeriform fluid and egress for powder suspended in aeriform fluid being provided by air duct 55 and outlet tube 74, respectively.

In the operation of the powder cloud generator of the invention, after a supply of developer powder is placed in the hopper 93 and on the powder carrier element 28, the closure plate 103 is secured in position and the inlet duct 55 is connected to a source of pressurized aeriform fluid. As the shaft 22 is rotated in the direction indicated by the arrow in FIG. 2, shaft 83 is also driven causing dispensing platform 86 to rotate within hopper 93. As the dispensing platform is rotated, a small quantity of powder carried by the dispensing platform on the support surface thereof is permitted to pass under metering blade 96. This powder which has thus been metered by metering blade 96 is then deflected by dispensing blade 97 to the periphery of the support surface through the powder outlet in the wall of the hopper to fall by gravity through the powder discharge opening in the bearing bracket onto the powder carrier element 28 in front of meter blade 35.

As the powder carrier element 28 is rotated by means of shaft 22, a small quantity of powder carried by the support is permitted to pass under the meter blade while the remainder of the supply of powder is retained against the face of the meter blade. Brush 37, mounted next in line to meter blade 35 in the direction of rotation of the powder carrier element, agitates the powder sufficiently to prevent caking of the powder and to fluff up the powder particles so that a substantially uniform textured powder is delivered to meter blade 36 where it is remetered, excess powder being deflected to one side of the powder carrier element to be returned by it to meter blade 35. Brush 38 agitates the powder particles which have been passed under meter blade 36 before it is picked up by the stream of compressed aeriform fluid as it flows through output orifices 76 to be delivered through outlet tube 74.

Since it is undesirable to permit too large a quantity of powder to build up in front of meter blade 35, or, on the other hand, to permit no powder supply to remain in front of meter blade 35, it is apparent that the quantity of powder delivered by the powder dispenser should be approximately equal to the powder output from the powder cloud generator.

Although it has been found preferable to position the metering blade 96 approximately between the range of ,6 of an inch to V of an inch above the powder support for metering sub-micron sized developer powder, it is apparent that this spacing can be modified depending upon the particle size of the material to be dispensed and a the quantity to be dispensed.

In FIG. 6 there is illustrated another embodiment of a powder dispenser adapted to feed powder to a powder cloud generator having a modified cover plate thereon to support the powder dispenser elements. In this embodiment the powder cloud generator is similar to the one illustrated in FIGS. 2 to 5, inclusive, except for its cover plate. As shown, the open end or top of casing 20 is enclosed by cover plate attached thereto by bolts 62 and sealed by O-ring gasket 64. Cover plate 120 is counterbored as at 121 to receive bearings 23 held in place by thrust ring 122 secured by screws 123.

The top portion of the cover plate has bore 124 formed therein concentric with counterbore 121, which is adapted to receive the bottom reduced portion of hopper 125. Hopper 125 consists of tube 126 having an annular flange 127 attached thereto, as by welding, and a cap plate 128 secured to the upper portion thereof in a similar manner. The hopper 125 is closed at its upper end by threaded closure plate 103 and sealed by gasket 104 positioned in a suitable annular groove in the cap plate to be engaged by the flanged portion of closure plate 103. Bolts 62 passing through suitable bolt holes in flange 127 are used to secure hopper 125 to cover plate 126 with O-ring gasket 107 secured therebetween.

To support a column of powder within hopper 125 there is provided a dispensing platform 132, circular in form, secured by set screws 134 to shaft 131 journaled in bearings 23 for rotation within tube 126, the annular flat surface of the dispensing platform forming a powder support 133 for the powder to be dispensed as the powder support is rotated beneath metering blade 96 and dispensing blade 97 mounted within tube 126.

To drive shaft 131 there is provided a cog wheel 135 secured to the bottom of the shaft by set screws 134, the shaft being biased downward by means of cup spring 136 positioned on the shaft between cog wheel 135 and the bottom surface of cover plate 120. Cog Wheel 135, consisting of hub 137 having pins or teeth 138 secured around 8 its peripheral edge, is positioned so that the pins 138 will be engaged by vertical pins 34 on shell 33 as it is rotated.

Metering blade 96 and dispensing blade 97 are secured to the inner cylindrical wall of tube 126 by means of screws 95 passing through suitable elongated apertures in the tube and threaded into these blades. The apertures in the tube are sealed by suitable cup washers 141 and gaskets 142 encircling the screw bodies between the screw heads and the wall of tube 126.

Powder deflected from the surface of powder support 133 is directed by dispensing blade 37 through powder outlet 143 formed in the bottom wall portion of tube 126 from whence it will fall through powder discharge opening 144 located in cover plate 12f) directly beneath powder outlet 143. Additional powder discharge openings, 144 are formed in cover plate 120 beneath the peripheral edge of dispensing platform 132 to permit the small quantity of powder, which may fall from the dispensing platform during operation, to drop onto powder carrier element 28 rather than accumulating between the dispensing platform and the cover plate where it may interfere with the rotation of the dispensing platform.

The cover plate 120 is provided with a threaded opening 68 to receive cylinder 145 adjustably secured by lock nut 146 and sealed by gaskets 72 and 73 held in suitable annular recesses formed in the lock nut. A modified form of pick-up tube 147 having an inner conical output orifice 143 formed therein is secured within the bottom portion of the cylinder by fastener 151, and a discharge conduit 152 is secured in the top of the cylinder in alignment with the bored output opening 153 formed therein.

The operation of the powder dispenser shown in FIG. 6 is the same as that previously described in relation to FIGS. 2 to 5, inclusive.

While there have been shown and described the fundamental novel features of the invention as applied to a preferred embodiment, it will be understood that various omissions and substitutions and changes in the form and details of the device illustrated and in its operation may be made by those skilled in the art, without departing from the spirit of the invention, as, for example, by providing a separate drive motor for the powder dispenser. It is the intention, therefore, to be limited only as indicated by the scope of the following claims.

What is claimed is:

1. A powder cloud generator including an enclosure, a powder carrier means, including a support and a shaft, rotatably journaled in the bottom portion of said enclosure with said support positioned for rotation in a horizontal plane and with said shaft extending from said enclosure for connection to a suitable drive means; metering means connected to said enclosure and positioned therein in closely spaced relation above said support to meter a quantity of .a powder over said support as it is rotated beneath said metering means, an output means connected to said enclosure with one end of said output means positioned in closely spaced relation above said support, the opposite end of said output means being connectable to a discharge conduit, an inlet duct in said enclosure adapted to be connected to a source of compressed aeriform fluid, a powder inlet duct in said enclosure positioned above said support, a powder dispenser connected to said enclosure and positioned over said powder inlet duct, said powder dispenser including a reservoir means for powder material, a dispensing means positioned in said reservoir, said powder carrier means being operatively connected to said dispensing means to effect operation of said dispensing means to feed powder through said powder inlet duct onto said powder carrier means between said output means and said metering means in the direction of rotation of said support when said powder carrier means is rotated.

2. A powder cloud generator including an enclosure, a powder carrier means, including a shaft, rotatably journaled in said enclosure, a support connected to one end of said shaft and positioned for rotation in a horizontal plane within said enclosure, the opposite end of said shaft being connectable to a source of power; metering means connected to said enclosure and positioned therein in closely spaced relation .above said support to meter a quantity of a powder over said support as it is rotated beneath said metering means, an output means connected to said enclosure with one end of said output means positioned in closely spaced relation above said support, the opposite end of said output means being connectable to a discharge conduit, an inlet duct in said enclosure adapted to be connected to a source of compressed aeriform fluid, a powder inlet duct in said enclosure positioned over said powder carrier means between said output means and said metering means in the direction of rotation of said support when said powder means is rotated, a powder dispenser connected to said enclosure over said powder inlet duct to form an airtight enclosure, said powder dispenser including a powder output duct in the bottom thereof, a powder reservoir means, a powder dispensing means positioned within said reservoir, said powder carrier means being operatively connected to said powder dispensing means to effect operation of said dispensing means whereby powder from a supply of powder in said powder reservoir means is uniformly fed through said powder inlet duct onto said powder carrier means.

3. A powder cloud generator including an enclosure, a powder carrier means, including a support, rotatably journaled in said enclosure with said support positioned for rotation in a horizontal plane; metering means connected to said enclosure and positioned therein in closely spaced relation above said support to meter a quantity of a powder over said support as it is rotated beneath said metering means, an output means connected to said enclosure with one end of said output means positioned in closely spaced relation to said support for removing powder therefrom, the opposite end of said output means being connectable to a discharge conduit, an inlet duct in said enclosure adapted to be connected to a source of compressed aeriform fluid, a powder inlet duct in said enclosure, and a powder dispenser connected to said enclosure and positioned over said powder inlet duct, said powder dispenser including a hopper means for powder material, said hopper means having an open bottom end and a powder outlet in the lower portion of a side wall thereof in communication with the interior of said enclosure, a powder dispensing platform operatively connected to said powder carrier means and positioned for rotation within said hopper means adjacent said powder outlet duct, a metering blade connected to said hopper means above said dispensing platform with its bottom edge spaced above said dispensing platform to meter a uniform quantity of powder to said dispensing platform as said dispensing platform is rotated therebeneath, a dispensing blade connected to said hopper means adjacent said powder outlet with its bottom edge positioned above said dispensing platform whereby powder, on said dispensing platform as it passes therebeneath, is deflected along said dispensing blade to the periphery of said dispensing platform through said powder outlet from whence it will fall through said powder inlet duct onto said powder carrier means between said output means and 10 said metering means in the direction of rotation of said support when said powder carrier means is rotated.

4. A dispenser for granular material including a support means having a powder discharge opening therein, a powder hopper open at both ends positioned above said support means with one end of said powder hopper attached to said support means, a shaft journal-ed in said support means, a dispensing platform having a powder support surface thereon connected to one end of said shaft positioned for rotation within said powder hopper, the opposite end of said shaft being connectable to a source of power, a metering blade connected to said powder hopper above said dispensing platform, the bottom edge of said metering blade being spaced above said support surface to meter a uniform amount of a powder to said support surface as said support surface rotates therebeneath, said powder hopper having a powder outlet through its side wall opposite said support surface and adjacent said metering blade, a dispensing blade connected to said powder hopper adjacent said opening with its bottom edge positioned above said support surface in close proximity thereto whereby powder on said support surface as it passes therebeneath is deflected along said dispensing blade to the periphery of the support surface, through said powder outlet from whence it will fall through said powder discharge opening.

5. A dispenser for granular material including a support, a bearing bracket having a powder discharge opening therein connected to said support, a powder hopper open at both ends positioned above said bearing bracket with one end of said powder hopper attached to said bearing bracket, a shaft journaled in said bearing bracket, a dispensing platform having a powder support surface thereon connected to one end of said shaft positioned for rotation in a horizontal plane Within said powder hopper, the opposite end of said shaft being connectable to a source of power, a metering blade connected to said powder hopper above said dispensing platform, the bottom edge of said metering blade being spaced above said support surface to meter a uniform amount of a powder to said support surface as said support surface rotates therebeneath, a dispensing blade connected to said powder hopper adjacent to and behind said metering blade in relation to the direction of rotation of said support with the bottom edge of said dispensing blade positioned above said support surface in close proximity thereto, said powder hopper having a powder outlet in its side wall opposite said support surface and adjacent said dispensing blade, whereby powder on said support surface after it passes beneath said metering blade is deflected along said dispensing blade to the periphery of the support surface, through said powder outlet from whence it will fall through said powder discharge opening.

References Cited in the file of this patent UNITED STATES PATENTS 2,619,256 Wiley Nov. 25, 1952 2,668,388 Thompson Feb. 9, 1954 2,750,073 Coffman June 12, 1956 2,812,883 Hayford Nov. 12, 1957 2,862,646 Hayford et a1. Dec. 2, 1958 

1. A POWER CLOUD GENERATOR INCLUDING AN ENCLOSURE, A POWDER CARRIER MEANS, INCLUDING A SUPPORT AND A SHAFT, ROTATABLY JOURNALED IN THE BOTTOM PORTION OF SAID ENCLOSURE WITH SAID SUPPORT POSITIONED FOR ROTATION IN A HORIZONTAL PLANE AND WITH SAID SHAFT EXTENDING FROM SAID ENCLOSURE FOR CONNECTION TO A SUITABLE DRIVE MEANS; METERING MEANS CONNECTED TO SAID ENCLOSURE AND POSITIONED THEREIN IN CLOSELY SPACED RELATION ABOVE SAID SUPPORT TO METER A QUANTITY OF A POWDER OVER SAID SUPPORT AS IT IS ROTATED BENEATH SAID METERING MEANS, AN OUTPUT MEANS CONNECTED TO SAID ENCLOSURE WITH ONE END OF SAID OUTPUT MEANS POSITIONED IN CLOSELY SPACED RELATION ABOVE SAID SUPPORT, THE OPPOSITE END OF SAID OUTPUT MEANS BEING CONNECTABLE TO A DISCHARGE CONDUIT, AN INLET DUCT IN SAID ENCLOSURE ADAPTED TO BE CONNECTED TO A SOURCE OF COMPRESSED AERIFORM FLUID 